Power transmission apparatus

ABSTRACT

The power transmission apparatus includes: a gear chamber, used for accommodating gears disposed on a rotating shaft used for transmitting power to a drive wheel; a clutch chamber, disposed adjacent to the gear chamber in an axial direction of the rotating shaft, and used for accommodating a clutch used for disconnecting or connecting the power transmitted by the rotating shaft to the drive wheel; and a communicating hole, used for communicating the clutch chamber with the gear chamber, where an inclined surface facing toward the communicating hole is provided on an inner surface inside the clutch chamber opposite to an outer peripheral surface of the clutch.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan application serialno. 2017-099881, filed on May 19, 2017. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The disclosure relates to a power transmission apparatus mounted on avehicle and used for transmitting power from a drive source such as anengine to a drive wheel.

2. Description of Related Art

A power transmission apparatus is used for transmitting power from adrive source such as an engine to a drive wheel in a vehicle. Forexample, as shown in Patent Document 1, a power transmission apparatusincludes: a gear mechanism, including a drive bevel gear (pinion gear),integrally rotating with a drive shaft extending along a front-to-reardirection of the vehicle, and a driven bevel gear (ring gear), engagedwith the drive bevel gear; a rotating shaft, disposed orthogonal to thedrive shaft, and integrally rotating with the driven bevel gear; andleft and right oil pressure clutches, disposed between left and rightends of the rotating shaft and axles connected to a pair of drivewheels.

In the power transmission apparatus of Patent Document 1, in an axialdirection of the rotating shaft, a gear chamber used for accommodatingthe gear mechanism is disposed in the center, and clutch chambers usedfor accommodating the left and right oil pressure clutches arerespectively disposed at two sides of the gear chamber. Moreover, thepower transmission apparatus includes an oil pump, and the oil pumpconveys oil stored in the gear chamber to the left and right oilpressure clutches. By using the oil pump, oil sucked from the gearchamber in the center is supplied to piston chambers of the clutches,and then are discharged into the clutch chambers at the two sides. Theoil discharged into the clutch chambers returns to the gear chamber inthe center through a communicating hole that communicates the clutchchambers with the gear chamber. That is, the power transmissionapparatus is a structure that circulates oil between the gear chamber inthe center and the left and right clutch chambers.

In the foregoing power transmission apparatus having an oil circulationstructure, especially in a situation where a temperature of the oil islow or viscosity is high, the following problems exist: the oil returnfrom the clutch chambers at the two sides to the gear chamber in thecenter is poor, and an oil surface of the gear chamber is difficult tobe kept at a higher position. Furthermore, because of a structure thatan oil strainer is disposed near the gear mechanism that is disposed inthe gear chamber in the center and that is used for transmitting power,once the oil surface of the gear chamber excessively decreases, theremay further be a risk that the oil sucked from a suction opening of theoil strainer is mixed with air (aeration).

[Patent Document 1]: Japanese Laid-open No. 2014-194242

SUMMARY OF THE INVENTION

The power transmission apparatus of an embodiment of the disclosure is apower transmission apparatus (100) mounted on a vehicle, andcharacterized by including: a rotating shaft (4), extending along awidth direction of the vehicle, and used for transmitting power to adrive wheel of the vehicle; gears (2, 3), disposed on the rotating shaft(4), and used for transmitting power to the rotating shaft (4); a clutch(5R or 5L), used for disconnecting or connecting the power transmittedby the rotating shaft (4) to the drive wheel; a gear chamber (15), usedfor accommodating the gears (2, 3), a clutch chamber (16 or 17),disposed adjacent to the gear chamber (15) in an axial direction of therotating shaft (4), and used for accommodating the clutch (5R or 5L);and a communicating portion (34 a or 35 a), used for communicating theclutch chamber (16 or 17) with the gear chamber (15), where an inclinedsurface (51 a or 52 a) facing toward the communicating portion (34 a or35 a) is provided on an inner surface of the clutch chamber (16 or 17)opposite to an outer peripheral surface of the clutch (5R or 5L).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams of an exterior structure of a powertransmission apparatus according to an embodiment of the disclosure,FIG. 1A is a top view, and FIG. 1B is a side view.

FIG. 2 is a perspective view of an exterior structure of a powertransmission apparatus.

FIG. 3 is a sectional view (a sectional view along A-A of FIG. 1A) of apower transmission apparatus.

FIG. 4 is a sectional view (a sectional view along B-B of FIG. 1B) of apower transmission apparatus.

FIGS. 5A and 5B are perspective views (partial sectional views) of aninterior structure of left and right clutch chambers and a gear chamber,FIG. 5A is a diagram of the left clutch chamber and a gear accommodatingportion of the gear chamber, and FIG. 5B is a diagram of the rightclutch chamber and a strainer accommodating portion of the gear chamber.

FIG. 6 is a perspective view (a partial sectional view) of an interiorstructure of a gear chamber (a gear accommodating portion and a straineraccommodating portion).

FIG. 7 is a sectional view of a communicating hole formed between aposition near a bottom portion of a right clutch chamber and a positionnear a bottom portion of a gear chamber (a strainer accommodatingportion).

FIG. 8 is a sectional view (a sectional view along P-P of FIG. 3) of aninterior structure of a gear chamber, a strainer chamber, and a rightclutch chamber.

DESCRIPTION OF THE EMBODIMENTS

The disclosure is directed to provide a power transmission apparatusthat can prevent an oil surface in the gear chamber from excessivelydecreasing by means of improving an oil return performance from clutchchambers to a gear chamber, and can effectively prevent oil sucked froma suction opening of an oil strainer from being mixed with air(aeration).

To achieve the objective, the power transmission apparatus of anembodiment of the disclosure is a power transmission apparatus (100)mounted on a vehicle, and characterized by including: a rotating shaft(4), extending along a width direction of the vehicle, and used fortransmitting power to a drive wheel of the vehicle; gears (2, 3),disposed on the rotating shaft (4), and used for transmitting power tothe rotating shaft (4); a clutch (5R or 5L), used for disconnecting orconnecting the power transmitted by the rotating shaft (4) to the drivewheel; a gear chamber (15), used for accommodating the gears (2, 3), aclutch chamber (16 or 17), disposed adjacent to the gear chamber (15) inan axial direction of the rotating shaft (4), and used for accommodatingthe clutch (5R or 5L); and a communicating portion (34 a or 35 a), usedfor communicating the clutch chamber (16 or 17) with the gear chamber(15), where an inclined surface (51 a or 52 a) facing toward thecommunicating portion (34 a or 35 a) is provided on an inner surface ofthe clutch chamber (16 or 17) opposite to an outer peripheral surface ofthe clutch (5R or 5L).

According to the power transmission apparatus of the disclosure, whenthe clutch rotates, oil in the clutch chamber is lifted upward along anouter peripheral surface of the clutch and along a rotating direction.In this case, because the inclined surface facing toward thecommunicating portion that communicates the clutch chamber with the gearchamber is provided on the inner surface of the clutch chamber oppositeto the outer peripheral surface of the clutch, the oil lifted along theouter peripheral surface of the clutch collides with the inclinedsurface. The oil collided with the inclined surface splashes toward thecommunicating portion. Therefore, most of the oil splashed at theinclined surface is introduced into the gear chamber through thecommunicating portion. In this way, the oil in the clutch chamber can beeffectively introduced into (return to) the gear chamber by means of oillift generated by the rotation of the clutch.

In addition, the power transmission apparatus may also be that thecommunicating portion (34 a or 35 a) is a communicating hole formed onwall portions (34, 35) between the gear chamber (15) and the clutchchamber (16 or 17), and the power transmission apparatus includes a rib(36 or 37) protruding from the wall portion lower than the communicatingportion (34 a or 35 a) toward the inside of the clutch chamber (16 or17).

This structure includes the rib protruding from the wall portion lowerthan the communicating portion toward the inside of the clutch chamber,therefore, the rib may be used for holding some of the oil splashed atthe inclined surface toward the communicating portion. That is, beforereaching the communicating portion, some of the oil splashed at theinclined surface toward the communicating portion constantly drops dueto its own weight. In this case, the rib may be used for holding theconstantly dropping oil and introducing the oil into the communicatingportion. Thereby, more oil is ensured to be oil that returns from theclutch chamber to the gear chamber through the communicating portion.

In addition, the power transmission apparatus may also include anothercommunicating portion (34 b) formed on the wall portion (34 or 35), andthe another communicating portion (34 b) is formed at a position of thewall portion (34 or 35) lower than the communicating portion (34 a) andthe rib (36).

This structure includes the another communicating portion, therefore,oil stored at the bottom portion of the clutch chamber can return to thegear chamber through the another communicating portion. Therefore, theoil surface of the gear chamber can be more effectively prevented fromdecreasing, so as to pursue rationalization of a volume of oil of eachcomponent inside the power transmission apparatus.

In addition, the power transmission apparatus may also be that theanother communicating portion (34 b) is formed at a position higher thanan oil surface (L2) of the gear chamber (15) when the power transmissionapparatus (100) operates.

According to this structure, the another communicating portion is formedat the position higher than the oil surface of the gear chamber when thepower transmission apparatus operates, therefore, when the powertransmission apparatus operates, the oil stored at the bottom portion ofthe clutch chamber can effectively return to the gear chamber throughthe another communicating portion. Therefore, by using this structure,oil moving to the clutch chamber along with the operation of the powertransmission apparatus is enabled to effectively return to the gearchamber, so as to pursue the rationalization of the oil surface (thevolume of the oil) of each component inside the power transmissionapparatus.

In addition, the power transmission apparatus may also include an oilpump (7) used for conveying oil stored in the gear chamber (15) to theclutch chamber (16 or 17), and an oil strainer (66) connected to the oilpump (7) is accommodated in the gear chamber (15).

This structure includes the oil pump used for conveying the oil storedin the gear chamber to the clutch chamber, therefore there is a riskthat the oil surface of the gear chamber decreases due to the operationof the oil pump. However, according to the disclosure, because theinclined surface of the structure is included, the oil in the clutchchamber can be introduced into (return to) the gear chamber by means ofthe oil lift generated by the rotation of the clutch. Therefore, the oilsurface of the gear chamber is effectively prevented from decreasing.

In addition, the gear chamber accommodates the gear disposed on therotating shaft and the oil strainer connected to the oil pump,therefore, especially in a situation in which a volume of the oilreturning to the gear chamber is not sufficient, there is a risk thatthe oil is mixed with the air (aeration) because the oil stored in thegear chamber is stirred due to the rotation of the gear. Therefore,there is a risk of generating the aeration, that is, a risk of suckingoil mixed with the air into the oil strainer. In view of this risk, inthe disclosure, because the inclined surface of the structure isincluded, the volume of the oil returning from the clutch chamber to thegear chamber can be ensured to be sufficient. Therefore, the risk ofgenerating the aeration may be effectively reduced.

In addition, the power transmission apparatus may also be that the gearchamber (15) includes a gear accommodating portion (15 a) accommodatingthe gear (3) and a strainer accommodating portion (15 b) accommodatingthe oil strainer (66), the gear accommodating portion (15 a) and thestrainer accommodating portion (15 b) are disposed adjacent to eachother in the axial direction of the rotating shaft (4), and boundaryportions (15 c) of the gear accommodating portion and the straineraccommodating portion are in communication with each other; and thestrainer accommodating portion (15 b) is disposed at a side closer to acenter in the axial direction of the rotating shaft (4) than the gearaccommodating portion (15 a) disposed.

In addition, the power transmission apparatus may also be of thefollowing structure: a protruding portion (33) is formed on an innersurface of the strainer accommodating portion (15 b) near the boundaryportion (15 c); and the protruding portion (33) includes an inclinedsurface (33 a), and the inclined surface (33 a) is inclined in such amanner that its position becomes closer to a far side of a rotatingdirection of the gear (3) in a direction farther away from the boundaryportion (15 c).

According to this structure, the oil lifted by means of the rotation ofthe gear that rotates in the gear accommodating portion can beintroduced from the gear accommodating portion into the straineraccommodating portion. Therefore, oil in the gear accommodating portioncan be effectively separated from the gear, and be actively conveyed tothe strainer accommodating portion closer to the center in the gearchamber. In terms of the result, a volume of oil left in the gearaccommodating portion can be reduced, therefore, the volume of the oilintroduced from the clutch chamber into the gear accommodating portionthrough the communicating portion can be ensured to be more. Based onthe above, the oil moving to the clutch chamber by using the operationof the power transmission apparatus is enabled to effectively return tothe strainer accommodating portion, so as to pursue the rationalizationof the volume of the oil of each component inside the power transmissionapparatus.

In addition, the power transmission apparatus may also be that theclutch chambers (16, 17) are a pair of clutch chambers (16, 17)respectively disposed at two sides of the gear chamber (15) in the axialdirection of the rotating shaft (4), the communicating portion (34 a or35 a) respectively communicates the pair of clutch chambers (16, 17)with the gear chamber (15); and the inclined surface (51 a or 52 a) is apair of inclined surfaces (51 a, 52 a) correspondingly provided in thepair of clutch chambers (16, 17) respectively.

According to this structure, in the power transmission apparatus, theclutch chambers are respectively disposed at the two sides of the gearchamber, therefore, the oil introduced into the clutch chambers at thetwo sides can return to the gear chamber in the center by using theinclined surface and the communicating portion. Therefore, the oilsurface of the gear chamber can be effectively prevented fromdecreasing, so as to pursue the optimum of the oil surface (the volumeof the oil) of each component inside the power transmission apparatus.

In addition, symbols in the parentheses are shown for referring to thereference numerals of each element in the following embodiments.

According to the power transmission apparatus of the disclosure, bymeans of improving the oil return performance from the clutch chambersto the gear chamber, the oil surface in the gear chamber can beprevented from excessively decreasing, so as to effectively preventgenerating the aeration, that is, prevent oil with air from being suckedfrom the suction opening of the oil strainer.

The following describes embodiments of the disclosure with reference tothe accompanying drawings. FIGS. 1A and 1B are diagrams of an exteriorstructure of a power transmission apparatus according to an embodimentof the disclosure, FIG. 1A is a top view, and FIG. 1B is a side view.FIG. 2 is a perspective view of an exterior structure of a powertransmission apparatus. FIG. 3 and FIG. 4 are sectional views of thepower transmission apparatus, FIG. 3 is a sectional view along A-A ofFIG. 1A, and FIG. 4 is a sectional view along B-B of FIG. 1B.

As shown in FIG. 4 and the like, a power transmission apparatus 100 isconfigured as a differential mechanism used for allocating rotation of adrive shaft 1 to left and right wheels (not shown). The drive shaft 1 isconnected to a rear end of a propeller shaft not shown, and drive powerfrom a drive source (engine) not shown is transmitted to the drive shaft1. The power transmission apparatus 100 includes: a drive bevel gear(pinion gear) 2, used for integrally rotating with the drive shaft 1; adriven bevel gear (ring gear) 3, engaged with the drive bevel gear 2; acenter shaft (rotating shaft) 4, disposed orthogonal to the drive shaft1, and connected to the driven bevel gear 3 in a manner of integrallyrotating with the driven bevel gear 3; left and right oil pressureclutches 5L and 5R, disposed at the left and right of the center shaft4; left and right axles 6L and 6R, used for respectively transmittingdrive power transmitted by the left and right oil pressure clutches 5Land 5R to the left and right wheels (not shown); an oil pump (anelectric oil pump) 7, used for supplying hydraulic oil (oil) to eachpiston chamber 59L and 59R of the left and right oil pressure clutches5L and 5R; and left and right pressure regulating valves 8L and 8R, usedfor regulating pressure of oil discharged from each piston chamber 59Land 59R. In addition, the power transmission apparatus 100 includes acenter case 9 used for accommodating the differential mechanism, andside cases 58L and 58R used for respectively accommodating the left andright oil pressure clutches 5L and 5R. As shown in FIG. 1A and FIG. 2,the center case 9 is divided, by using a center of a front-to-reardirection, into two parts, namely, a front case 9 a and a rear case 9 b.The front case 9 a and the rear case 9 b are connected to each other inthe front-to-rear direction, and are integrally fixed by means of beingsecured by a bolt 96. The left and right side cases 58L and 58R areintegrally fixed at openings at left and right ends of the center case 9by means of being secured by a bolt 97 (referring to FIG. 1A). Inaddition, an axial direction of a rotating shaft or an axial directionin the following descriptions represents an axial direction of thecenter shaft 4 (a left-to-right direction in FIG. 1A). The followingfurther describes each structure.

The driven bevel gear 3 is mounted at an outer periphery of the centershaft 4 disposed on a common axis of the left axel 6L and the right axel6R. Therefore, when the drive shaft 1 is driven to rotate by using theengine and the propeller shaft, the drive power is transmitted from thedrive bevel gear 2 and the driven bevel gear 3 to the center shaft 4, soas to enable the center shaft 4 to rotate.

The center case 9 is internally provided with a gear chamber 15 disposedat a center of the axial direction of the center shaft 4. In addition,the left and right side cases 58L and 58R are respectively internallyprovided with a pair of clutch chambers 16 and 17 disposed at two sidesof the gear chamber 15. Therefore, a casing of the power transmissionapparatus 100 is of a structure of three chambers, that is, includingthe gear chamber 15 and the pair of clutch chambers 16 and 17.

The gear chamber 15 includes a gear accommodating portion 15 a and astrainer accommodating portion 15 b, the gear accommodating portion 15 ais a chamber provided with the driven bevel gear 3, and the straineraccommodating portion 15 b is a chamber provided with a part of thedrive bevel gear 2 and the oil strainer 66. The gear accommodatingportion 15 a is located on a left side in the gear chamber 15, andadjacent to a right side of the left clutch chamber 17. On the otherhand, the strainer accommodating portion 15 b is located on a right sidein the gear chamber 15, and adjacent to a left side of the right clutchchamber 16. The gear accommodating portion 15 a and the straineraccommodating portion 15 b communicate with each other at a boundaryportion 15 c therebetween (referring to FIG. 4 and FIG. 6), and the gearaccommodating portion 15 a and the strainer accommodating portion 15 bform the gear chamber 15.

As shown in FIG. 3 and the like, the left and right clutch chambers 16and 17 are respectively provided with the oil pressure clutch 5L and theoil pressure clutch 5R. The right oil pressure clutch 5R in the rightclutch chamber 16 includes: a clutch drum (clutch housing) 41R,approximately in a shape of a cylinder, and connected to a right endportion of the center shaft 4; a clutch hub 43R, spline-connected to anend portion of the right axel 6R at an inner peripheral side of theclutch drum 41R; and a friction binding portion 42R, formed by means ofalternately laminating multi-layers of friction material (plate) alongthe axial direction in the clutch drum 41R. In addition, a positionadjacent to the friction binding portion 42R is provided with: a pistonhousing 44R, integrally formed with the right side case 58R; a cylinderpiston 45R, accommodated in the piston housing 44R; and a return spring47R, used for applying a force to the cylinder piston 45R. The pistonhousing 44R is internally provided with a piston chamber 59R, and thehydraulic oil is introduced between the piston chamber 59R and thecylinder piston 45R. In addition, although detailed descriptions areomitted, the oil pressure clutch 5L disposed in the left clutch chamber17 is of a same structure as the oil pressure clutch 5R (Numerals ofelements of the oil pressure clutch 5L are marked with a suffix L).

As shown in FIG. 4 and the like, the electric oil pump 7 includes amotor portion 71 and a pump portion 72. The motor portion 71 generatesrotating power, and the pump portion 72 pumps the hydraulic oil (oil)sucked from the oil strainer 66 to the left and right oil pressureclutches 5L and 5R by using the rotating power. The pump portion 72 isof a structure of double pumps, that is, left and right internallyconnected gear pumps (oil pumps) 74L and 74R are serially connected toeach other on a pump shaft 73. Oil lines (not shown) extending to adownstream side to communicate with the left and right piston chambers59L and 59R of the left and right oil pressure clutches (clutchapparatuses) 5L and 5R are connected to the oil pumps 74L and 74R.Therefore, the left internally connected gear pump 74L pumps oil to thepiston chamber 59L of the left oil pressure clutch 5L, and the rightinternally connected gear pump 74R pumps oil to the piston chamber 59Rof the right oil pressure clutch 5R.

Left and right pressure regulating valves 8L and 8R are linear solenoidvalves (electromagnetic pressure regulating valves). As shown in FIG.1A, FIG. 1B, FIG. 2, and the like, the left and right pressureregulating valves 8L and 8R of this embodiment are mounted by means ofinserting into mounting holes (not shown) formed on the side cases 58Land 58R, and are approximately symmetrically disposed in right besideeach piston chamber 59L and 59R of the left and right oil pressureclutches 5L and 5R. Therefore, oil lines 67L and 67R from the left andright piston chambers 59L and 59R to the left and right pressureregulating valves 8L and 8R are respectively formed by using theshortest distances. In addition, the oil lines 67L and 67R between thepiston chambers 59L and 59R and the pressure regulating valves 8L and 8Rare provided with filters (secondly filter: purification component) 40Land 40R used for removing little foreign matter contained in thehydraulic oil flowing on the oil lines 67L and 67R.

In addition, the side cases 58L and 58R are internally provided withlube oil lines 60L and 60R used for introducing oil ejected from thepressure regulating valves 8L and 8R into the inside of the oil pressureclutches 5L and 5R. That is, in the power transmission apparatus 100 ofthis embodiment, the oil ejected from the pressure regulating valves 8Land 8R are directly introduced into the inside of the oil pressureclutches 5L and 5R by using the lube oil lines 60L and 60R, rather thanby using an oil line (an axis oil line) formed inside the center shaft4, and then the introduced oil are stirred by means of rotation ofclutch hubs 43L and 43R, so as to lubricate rotating slide portions ofthe oil pressure clutches 5L and 5R.

In addition, the oil strainer 66 is disposed near a bottom portion 15 d(referring to FIG. 3) of the gear chamber 15. A lower surface of the oilstrainer 66 is provided with a suction opening 66 a used for suckinghydraulic oil, so as to suck hydraulic oil stored in the bottom portion15 d in the gear chamber 15 through the suction opening 66 a.

In addition, the left and right piston chambers 59L and 59R are providedwith oil pressure sensors 90L and 90R used for detecting oil pressure ofoil in the piston chambers 59L and 59R. The oil pressure sensors 90L and90R are mounted by means of inserting a sensor portion at a root portioninto another mounting hole (not shown) formed on the side cases 58L and58R. The oil pressure sensors 90L and 90R detect the oil pressure in thepiston chambers 59L and 59R by the sensor portions disposed in thepiston chambers 59L and 59R through the mounting holes. In addition,covers (protection components) 95L and 95R are provided to cover atleast one part of the pressure regulating valves 8L and 8R and the oilpressure sensors 90L and 90R that are exposed from the side cases 58Land 58R.

FIGS. 5A and 5B are perspective views (partial sectional views) of aninterior shape of the left and right clutch chambers 16 and 17 and thegear chamber 15, FIG. 5A is a diagram of an upper interior shape of theleft clutch chamber 17 and the gear accommodating portion 15 a of thegear chamber 15, and FIG. 5B is a diagram of an upper interior shape ofthe right clutch chamber 16 and the strainer accommodating portion 15 bof the gear chamber 15. In addition, FIG. 5A is a diagram of an exteriorportion (inner surfaces of the center case 9 (the rear case 9 b) and theleft side case 58L) of a part X1 shown in FIG. 2, and FIG. 5B is adiagram of an exterior portion (inner surfaces of the center case 9 (therear case 9 b) and the right side case 58R) of a part X2 shown in FIG.2.

As shown in FIG. 5A, the left clutch chamber 17 accommodates the clutchdrum 41L of the oil pressure clutch 5L. In addition, the left clutchchamber 17 communicates with the gear accommodating portion 15 a of theadjacent gear chamber 15 by using a communicating hole 35 a formed on anisolation wall (wall portion) 35. Moreover, in this embodiment, aportion in the left side case 58L forming the left clutch chamber 17opposite to an outer periphery of an upper side of the clutch drum 41Lis provided with an inclined wall 52 disposed opposite to an outerperipheral surface of the clutch drum 41L. An inner surface 52 a of theinclined wall 52 forms an inclined surface inclined to the followingdirection: in two sides with respect to a rotating direction R1 (atraveling direction of the outer peripheral surface of the clutch drum41L when the clutch drum 41L rotates) of the clutch drum 41L, one side(the right side of the figure) close to the gear chamber 15 (the gearaccommodating portion 15 a) is set to an inner side of the travelingdirection, and the other side (the left side of the figure) away fromthe gear chamber 15 is set to a front side. In addition, the inclinedwall 52 and the inclined surface 52 a are formed at a position oppositeto a portion (a portion rotating toward a rising direction duringrotation) that is closer to the front side in the rotating direction R1of the clutch drum 41L than an upper end (a top portion) of the clutchdrum 41L is. In addition, the communicating hole 35 a is formed on anisolation wall 35 in approximately right beside the gear chamber 15 ofthe inclined wall 52 (the inclined surface 52 a). The inclined wall 52(the inclined surface 52 a) is formed as a surface facing toward thecommunicating hole 35 a.

In addition, in this embodiment, a protruding rib 37 facing toward theinside of the left clutch chamber 17 and protruding toward a horizontaldirection is formed at a position on the isolation wall 35 lower thanthe communicating hole 35 a. The rib 37 includes a plate portionprotruding from a surface of the left clutch chamber 17 of the isolationwall 35 toward the horizontal direction (toward the left side of thefigure). That is, the rib 37 is formed as a protrusion at a lower sideof the communicating hole 35 a and extending from the isolation wall 35to the left side. In addition, the communicating hole 35 a and the rib37 are formed at a position opposite to an upper side of a half (anupper half part) of the clutch drum 41L. In addition, an end portion ofthe rib 37 extends to near an end surface (an end surface in the axialdirection) of the gear chamber 15 of the clutch drum 41L. Therefore, anoil storage portion 37 a used for temporarily storing (keeping) oillifted by the clutch drum 41L is formed at an upper surface of the rib37.

In the left clutch chamber 17, when the clutch drum 41L rotates, oilstored in a bottom portion 17 a (referring to FIG. 3) of the left clutchchamber 17 is stirred by using the clutch drum 41L. The stirred oil islifted upward along the outer peripheral surface of the clutch drum 41Land along the rotating direction R1 of the clutch drum 41L. In thiscase, because the inclined wall 52 (the inclined surface 52 a) of thestructure is included, the oil lifted along the outer peripheral surfaceof the clutch drum 41L collides with the inclined wall 52 (the inclinedsurface 52 a). The oil splashes at the inclined surface 52 a toward thecommunicating hole 35 a. Therefore, as shown by an arrow S1 in FIG. 5A,most of the oil splashed at the inclined surface 52 a is introduced intothe gear chamber 15 through the communicating hole 35 a. In this way,the oil in the left clutch chamber 17 can return to the gear chamber 15(the gear accommodating portion 15 a) by means of oil lift generated bymeans of the rotation of the clutch drum 41L.

In addition, the rib 37 is formed in the left clutch chamber 17,therefore, the rib 37 may be used for holding some of the oil splashedat the inclined surface 52 a toward the gear chamber 15. That is, beforereaching the communicating hole 35 a, some of the oil splashed at theinclined surface 52 a toward the gear chamber 15 constantly drops due toits own weight. In this case, the rib 37 may be used for holding theconstantly dropping oil and introducing the oil into the communicatinghole 35 a. Thereby, more oil is ensured to be oil that returns from theleft clutch chamber 17 to the gear chamber 15 (the gear accommodatingportion 15 a) through the communicating hole 35 a.

In addition, as shown in FIG. 5B, the right clutch chamber 16accommodates the clutch drum 41R of the oil pressure clutch 5R. Inaddition, the right clutch chamber 16 communicates with the straineraccommodating portion 15 b of the adjacent gear chamber 15 by using acommunicating hole 34 a forming on the isolation wall (wall portion) 34.Moreover, in this embodiment, an outer peripheral side of the clutchdrum 41R in the right side case 58R forming the right clutch chamber 16is provided with an inclined wall 51 disposed opposite to an outerperipheral surface of the clutch drum 41R. An inner surface 51 a of theinclined wall 51 forms an inclined surface inclined to the followingdirection: in two sides with respect to a rotating direction R2 (atraveling direction of the outer peripheral surface of the clutch drum41R when the clutch drum 41R rotates) of the clutch drum 41R, one side(the left side of the figure) close to the gear chamber 15 is set to aninner side (an upper side) of the traveling direction, and the otherside (the right side of the figure) away from the gear chamber 15 is setto a front side (a lower side). In addition, the communicating hole 34 ais formed on the isolation wall 34 lower than the location right besidethe gear chamber 15 of the inclined wall 51 (the inclined surface 51 a).The inclined wall 51 (the inclined surface 51 a) is formed as a surfacefacing toward the isolation wall 34 and communicating hole 34 a.

In addition, in this embodiment, a protruding rib 36 facing toward theinside of the right clutch chamber 16 and protruding toward a horizontaldirection is formed at a position on the isolation wall 34 lower thanthe communicating hole 34 a. The rib 36 includes a plate portionprotruding from a surface of the right clutch chamber 16 of theisolation wall 34 toward the horizontal direction (toward the right sideof the figure). That is, the rib 36 is formed as a protrusion at a lowerside of the communicating hole 34 a and extending from the isolationwall 34 to the right side. In addition, the communicating hole 34 a andthe rib 36 are formed at a position at a lower side (a lower position)than the inclined wall 51, and opposite to an upper side of a half (anupper half part) of the clutch drum 41R. In addition, an end portion ofthe rib 36 extends to near an end surface (an end surface at the leftside of the axial direction) of the gear chamber 15 of the clutch drum41R. Therefore, an oil storage portion 36 a used for temporarily storing(keeping) oil lifted by the clutch drum 41R is formed at an uppersurface of the rib 36.

In the right clutch chamber 16, when the clutch drum 41R rotates, oilstored in a bottom portion 16 a (referring to FIG. 3) of the rightclutch chamber 16 is lifted by using the clutch drum 41R. The lifted oilsplashes upward along the outer peripheral surface of the clutch drum41R and along the rotating direction R2 of the clutch drum 41R. In thiscase, because the inclined wall 51 (the inclined surface 51 a) of thestructure is included, the oil lifted along the outer peripheral surfaceof the clutch drum 41R collides with the inclined wall 51 (the inclinedsurface 51 a). The oil splashes at the inclined surface 51 a toward theisolation wall 34. When colliding with the isolation wall 34, thesplashed oil flows downward along a surface of the isolation wall 34, soas to reaching the communicating hole 34 a. In this way, the oil isintroduced into the gear chamber 15 through the communicating hole 34 a.Therefore, as shown by an arrow S2 in FIG. 5B, the oil splashed at theinclined surface 51 a is introduced into the gear chamber 15 (thestrainer accommodating portion 15 b) through the communicating hole 34a. In this way, the oil in the right clutch chamber 16 can return to thegear chamber 15 by means of oil lift generated by means of the rotationof the clutch drum 41R.

In addition, the rib 36 is formed in the right clutch chamber 16,therefore, the rib 36 may be used for holding some oil flowing downwardalong the surface of the isolation wall 34, and introducing the oil intothe communicating hole 34 a. Thereby, more oil is ensured to be oil thatreturns from the right clutch chamber 16 to the gear chamber 15 throughthe communicating hole 34 a.

FIG. 6 is a perspective view (a partial sectional view) of an interiorshape of the gear chamber 15 (the gear accommodating portion 15 a andthe strainer accommodating portion 15 b), and is a diagram of aninterior portion (inner surfaces of the rear case 9 b of the center case9) of a part Y shown in FIG. 2. As shown in FIG. 6, a protruding portion33 that protrudes an inner surface of the strainer accommodating portion15 b is formed at a boundary portion 15 c between the inner surface ofthe strainer accommodating portion 15 b of the gear chamber 15 and thegear accommodating portion 15 a. The protruding portion 33 is formed ata position opposite to a portion rotating toward a rising direction whenthe driven bevel gear 3 in the gear accommodating portion 15 a rotates.In addition, the protruding portion 33 is in a shape of an inclinedsurface inclined in such a manner that a height position of a lower sidesurface 33 a becomes higher in a direction farther away from theboundary portion 15 c. That is, the protruding portion 33 can introduce,by means of making the lower side surface 33 a be in the shape describedabove, most of the oil lifted along with the rotation of the drivenbevel gear 3 (not shown in FIG. 6) from the gear accommodating portion15 a to the strainer accommodating portion 15 b as shown by an arrow S3.The driven bevel gear 3 rotates in the gear accommodating portion 15 aabout a rotating direction R3 shown in FIG. 6. Therefore, as shown bythe arrow S3, the oil lifted by means of the rotation of the drivenbevel gear 3 that rotates in the gear accommodating portion 15 a can beeffectively separated from the driven bevel gear 3, and be activelyintroduced into the strainer accommodating portion 15 b closer to thecenter in the gear chamber 15. Thereby, a volume of oil left in the gearaccommodating portion 15 a can be reduced, and a volume of the oilintroduced from the left clutch chamber 17 into the gear chamber 15 (thegear accommodating portion 15 a) through the communicating hole 35 adescribed above can be ensured to be more. Based on the above, the oilmoving to the left clutch chamber 17 is enabled to effectively return tothe strainer accommodating portion 15 b of the gear chamber 15 by usingthe operation of the power transmission apparatus 100, so as to pursuethe rationalization of the oil surface (the volume of the oil) of eachcomponent inside the power transmission apparatus 100.

FIG. 7 is a perspective view (a sectional view) of the communicatinghole 34 b formed between the bottom portion 16 a of the right clutchchamber 16 and the bottom portion 15 d of the gear chamber 15 (thestrainer accommodating portion 15 b). In addition, FIG. 7 is a diagramof an interior portion (the inner surfaces of the center case 9 and theright side case 58R) of a part Z shown in FIG. 2. As shown in FIG. 7, inthe center case 9, besides the communicating hole 34 a, a communicatinghole 34 b (another communicating portion) is additionally formed at aheight position near a lower end of the isolation wall 34. Thecommunicating hole 34 b communicates the bottom portion 15 d of thestrainer accommodating portion 15 b of the gear chamber 15 or a positionnear the bottom portion 15 d with the bottom portion 16 a of the rightclutch chamber 16 or a position near the bottom portion 16 a that areseparated by the isolation wall 34.

In addition, FIG. 7 shows an oil surface L1 of the right clutch chamber16 and an oil surface L2 of the strainer accommodating portion 15 b ofthe gear chamber 15 when the power from the engine is transmitted to theleft and right wheels by using the power transmission apparatus 100(when the clutch drum 41R, or the drive bevel gear 2, the driven bevelgear 3, and the like rotate). As shown in FIG. 7, when the powertransmission apparatus 100 transmits the power to the left and rightwheels, oil circulates in the components of the power transmissionapparatus 100. Therefore, compared with the oil surface L2 of thestrainer accommodating portion 15 b, the oil surface L1 of the rightclutch chamber 16 is in a higher position. In this case, it is ideal toset the position (the height position) of the communicating hole 34 b ata position higher than the oil surface L2 of the gear chamber 15 (thestrainer accommodating portion 15 b) when the power is transmitted toleft and right wheels. If such a setting is applied, when the powertransmission apparatus 100 transmits the power to the left and rightwheels, as shown by an arrow S4 in FIG. 7, the oil stored in the bottomportion 16 a of the right clutch chamber 16 is enabled to effectivelyreturn to the strainer accommodating portion 15 b through thecommunicating hole 34 b. Therefore, by using this structure, oil movingto the right clutch chamber 16 along with the operation of the powertransmission apparatus 100 is enabled to effectively return to thestrainer accommodating portion 15 b of the gear chamber 15, so as topursue the rationalization of the oil surface (the volume of the oil) ofeach component inside the power transmission apparatus 100.

FIG. 8 is a perspective view (a partial sectional view) of the bottomportion 15 d of the gear chamber 15 and the bottom portion 16 a of theright clutch chamber 16. In addition, FIG. 8 is a diagram of a partcorresponding to a sectional view indicated by P-P of FIG. 3. As shownin FIG. 8, in this embodiment, the right clutch chamber 16 does notdirectly communicate with the gear accommodating portion 15 a of thegear chamber 15 due to the isolation of the wall portion 39 of thecenter case 9. On the other hand, the right clutch chamber 16communicates with the strainer accommodating portion 15 b of the gearchamber 15. That is, a communicating hole (a communicating portion) 38 aformed by a through hole is provided, the through hole runs through afront end of the right clutch chamber 16, a front end of the straineraccommodating portion 15 b of the gear chamber 15 and a position near alower end of a wall portion 38, and the communicating hole 38 a is usedfor communicating the right clutch chamber 16 with the straineraccommodating portion 15 b of the gear chamber 15.

Assuming that a wall portion 39 between the right clutch chamber 16 andthe gear accommodating portion 15 a of the gear chamber 15 is providedwith a communicating hole or the like to enable the right clutch chamber16 and the gear accommodating portion 15 a of the gear chamber 15directly communicate with each other, oil in the right clutch chamber 16may be forced and introduced into the gear accommodating portion 15 a ofthe gear chamber 15 through the communicating hole due to the rotationof the driven bevel gear 3, causing a risk of excessively decreasing ofthe oil surface in the right clutch chamber 16. In view of this risk, inthis embodiment, the right clutch chamber 16 is not in directcommunication with the gear accommodating portion 15 a of the gearchamber 15. Therefore, oil may be prevented from being introduced due tothe rotation of the driven bevel gear 3, so as to effectively preventthe oil surface in the right clutch chamber 16 from excessivelydecreasing.

On the other hand, in this embodiment, a communicating holecommunicating the right clutch chamber 16 with the gear accommodatingportion 15 a of the gear chamber 15 is not provided, consequently, thefollowing undesirable situation may occur: when oil in the powertransmission apparatus 100 is exchanged, the oil cannot be smoothlydischarged from the right clutch chamber 16 to the gear chamber 15through the communicating hole. However, in view of this, in thisembodiment, the communicating hole 38 a communicating the right clutchchamber 16 with the strainer accommodating portion 15 b of the gearchamber 15 is provided, and a diameter of the communicating hole 38 a isset to be a larger diameter, so as to ensure to discharge the oil fromthe right clutch chamber 16 to the gear chamber 15 when the oil isexchanged.

The following simply describes flowing and actions of oil in a powertransmission apparatus 100 of this embodiment. In the power transmissionapparatus 100, oil stored in a bottom portion 15 d of a gear chamber 15(a strainer accommodating portion 15 b) is sucked from an oil strainer66 into left and right oil pumps 74L and 74R by means of rotation of anoil pump 7 (the left and right oil pumps 74L and 74R) driven by a motorportion 71. The oil sucked into the left and right oil pumps 74L and 74Ris introduced into left and right piston chambers 59L and 59R of leftand right oil pressure clutches (clutch apparatuses) 5L and 5R at adownstream side. Pressure of the oil introduced into the left and rightpiston chambers 59L and 59R is regulated by left and right pressureregulating valves 8L and 8R disposed at a downstream side of eachflowing direction of oil of the left and right oil pressure clutches 5Land 5R. The oil flowing out of the left and right pressure regulatingvalves 8L and 8R is supplied to the inside of the oil pressure clutches5L and 5R by using lube oil lines 60L and 60R extending from the leftand right pressure regulating valves 8L and 8R to the downstream side,to lube the oil pressure clutches 5L and 5R and the like. The oilsupplied to the oil pressure clutches 5L and 5R is stored in bottomportions 16 a and 17 a of clutch chambers 16 and 17. The oil stored inthe bottom portions 16 a and 17 a of the clutch chambers 16 and 17returns to the gear chamber 15 through communicating holes 34 a and 35 aby means of lift generated by rotation of the clutches 5L and 5R.

As described above, driven by the motor portion 71, the left and rightoil pumps 74L and 74R eject oil. However, if the left and right pressureregulating valves 8L and 8R are open, the oil ejected from the left andright oil pumps 74L and 74R directly passes through the left and rightpiston chambers 59L and 59R. Therefore, the left and right oil pressureclutches 5L and 5R are not connected. On the other hand, if the left andright pressure regulating valves 8L and 8R are closed in a specificdegree, oil pressure of the left and right piston chambers 59L and 59Rat an upstream side increases, and the left and right oil pressureclutches 5L and 5R are connected with specific connecting force, totransmit drive power to left and right axles 6L and 6R.

As described above, according to the power transmission apparatus 100 ofthis embodiment, inclined walls 51 and 52 facing toward thecommunicating holes 34 a and 35 a that communicate the clutch chambers16 and 17 with the gear chamber 15 are disposed on inner surfaces in theclutch chambers 16 and 17 opposite to outer peripheral surfaces ofclutch drums 41L and 41R (the clutches 5L and 5R). Therefore, when theclutch drums 41L and 41R (the clutches 5L and 5R) rotate, the oil in theclutch chambers 16 and 17 is lifted along the outer peripheral surfacesof the clutch drums 41L and 41R and along the rotating directions of theclutch drums 41L and 41R. In this case, because inclined surfaces 51 aand 52 a are included, the oil lifted along the outer peripheralsurfaces of the clutch drums 41L and 41R collides with the inclinedsurfaces 51 a and 52 a. The oil colliding with the inclined surfaces 51a and 52 a splashes at the inclined surfaces 51 a and 52 a toward thecommunicating holes 34 a and 35 a. Therefore, most of the oil splashedat the inclined surfaces 51 a and 52 a is introduced into the gearchamber 15 through the communicating holes 34 a and 35 a. In this way,the oil in the clutch chambers 16 and 17 can be effectively introducedinto (return to) the gear chamber 15 by means of oil lift generated bythe rotation of the clutches 5L and 5R.

In addition, in the power transmission apparatus 100, because ribs 36and 37 protruding from the wall portions 34 and 35 lower than thecommunicating holes 34 a and 35 a toward the inside of the clutchchambers 16 and 17 are included, the ribs 36 and 37 may be used forholding some of the oil splashed at the inclined surfaces 51 a and 52 atoward the communicating holes 34 a and 35 a. That is, before reachingthe communicating holes 34 a and 35 a, some of the oil splashed at theinclined surfaces 51 a and 52 a constantly drops due to its own weight.In this case, the ribs 36 and 37 may be used for holding the constantlydropping oil and introducing the oil into the communicating holes 34 aand 35 a. Thereby, more oil is ensured to be oil that returns from theclutch chambers 16 and 17 to the gear chamber 15 through thecommunicating holes 34 a and 35 a.

In addition, in the power transmission apparatus 100, because the oilpump 7 used for conveying the oil stored in the gear chamber 15 to theclutch chambers 16 and 17 is included, there is a risk that the oilsurface of the gear chamber 15 decreases due to the operation of the oilpump 7. However, according to the power transmission apparatus 100 ofthis embodiment, because the inclined surfaces 51 a and 52 a of thestructure are included, the oil in the clutch chambers 16 and 17 can beintroduced into (return to) the gear chamber 15 by means of the oil liftgenerated by the rotation of the clutches 5L and 5R. Therefore, the oilsurface of the gear chamber 15 is effectively prevented from decreasing.

In addition, in the power transmission apparatus 100, the gear chamber15 accommodates the driven bevel gear 3 disposed on a center shaft 4 andthe oil strainer 66 connected to the oil pump 7, therefore, especiallyin a situation in which a volume of the oil returning to the gearchamber 15 is not sufficient, there is a risk that the oil is mixed withthe air (air bubble) because the oil stored in the gear chamber 15 isstirred due to the rotation of the driven bevel gear 3. Therefore, thereis a risk of generating the aeration, that is, a risk of sucking oilmixed with the air into the oil strainer 66 from a suction opening 66 a.In view of this risk, in the power transmission apparatus 100 of thisembodiment, because the inclined surfaces 51 a and 52 a of the structureare included, the volume of the oil returning from the clutch chambers16 and 17 to the gear chamber 15 can be ensured to be sufficient.Therefore, the oil surface of the gear chamber 15 may be prevented fromexcessively decreasing, and the risk of generating the aeration iseffectively reduced.

In addition, in the power transmission apparatus 100, the gear chamber15 includes the gear accommodating portion 15 a accommodating the drivenbevel gear 3 and the strainer accommodating portion 15 b accommodatingthe oil strainer 66, the gear accommodating portion 15 a and thestrainer accommodating portion 15 b are disposed adjacent to each otherin an axial direction of the center shaft 4, and boundary portions 15 cof the gear accommodating portion 15 a and the strainer accommodatingportion 15 b are in communication with each other. Moreover, thestrainer accommodating portion 15 b is disposed at a side closer to acenter in the axial direction of the center shaft 4 than the gearaccommodating portion 15 a disposed.

In addition, the structure may be that a protruding portion 33 is formedon an inner surface of the strainer accommodating portion 15 b near theboundary portion 15 c, the protruding portion 33 includes an inclinedsurface 33 a, and the inclined surface 33 a is inclined in such a mannerthat that its position becomes closer to a far side of the rotatingdirection of the driven bevel gear 3 in a direction farther away fromthe boundary portion 15 c.

According to this structure, the oil lifted along with the rotation ofthe driven bevel gear 3 that rotates in the gear accommodating portion15 a can be introduced into the strainer accommodating portion 15 b.Therefore, oil in the gear accommodating portion 15 a can be effectivelyseparated from the driven bevel gear 3, and be actively conveyed to thestrainer accommodating portion 15 b accommodating the oil strainer 66 inthe gear chamber 15. In terms of the result, a volume of oil left in thegear accommodating portion 15 a can be reduced, therefore, a volume ofthe oil introduced from the clutch chamber 17 into the gearaccommodating portion 15 a through the communicating hole 35 a can beensured to be more. Based on the above, the oil moving to the clutchchamber 17 along with the operation of the power transmission apparatus100 is enabled to effectively return to the strainer accommodatingportion 15 b, so as to pursue the rationalization of the volume of theoil of each component inside the power transmission apparatus 100.

In addition, in the power transmission apparatus 100, a communicatinghole 34 b formed on an isolation wall 34 between the right clutchchamber 16 and the strainer accommodating portion 15 b of the gearchamber 15 is further included, and the communicating hole 34 b isformed at a position on the isolation wall 34 lower than thecommunicating hole 34 b and the rib 36.

According to this structure, because the communicating hole 34 b isincluded, the oil stored in the bottom portion 16 a of the clutchchamber 16 is enabled to return to the gear chamber 15 (the straineraccommodating portion 15 b) through the communicating hole 34 b.Therefore, the oil surface of the gear chamber 15 (the straineraccommodating portion 15 b) is effectively prevented from decreasing, soas to pursue further rationalization of the volume of the oil of eachcomponent inside the power transmission apparatus 100.

In addition, in the power transmission apparatus 100, the communicatinghole 34 b is formed at a position higher than the oil surface L2 of thegear chamber 15 when the power transmission apparatus 100 operates.

According to this structure, when the power transmission apparatus 100operates, the oil stored in the bottom portion 16 a of the clutchchamber 16 is enabled to return to the gear chamber 15 through thecommunicating hole 34 b. Therefore, by using this structure, the oilmoving to the clutch chamber 16 along with the operation of the powertransmission apparatus 100 is enabled to effectively return to the gearchamber 15, so as to pursue the rationalization of the volume of the oilof each component inside the power transmission apparatus 100.

In addition, in the power transmission apparatus 100, the clutch chamberis a pair of clutch chambers 16 and 17 respectively disposed at twosides of the gear chamber 15 in the axial direction of the center shaft4, the communicating hole is a pair of communicating holes 34 a and 35a, respectively disposed at the pair of clutch chambers 16 and 17, andthe inclined surface is a pair of inclined surfaces 51 a and 52 arespectively disposed at the pair of clutch chambers 16 and 17.

According to this structure, in the power transmission apparatus 100 inwhich the two sides of the gear chamber 15 are respectively providedwith the clutch chambers 16 and 17, the oil introduced into the clutchchambers 16 and 17 at the two sides is enabled to effectively return tothe gear chamber 15 in the center by using the communicating holes 34 aand 35 a and the inclined surfaces 51 a and 52 a. Therefore, the oilsurface of the gear chamber 15 can be effectively prevented fromdecreasing, so as to pursue the optimum of the oil surface of eachcomponent inside the power transmission apparatus 100.

The foregoing describes the embodiments of the disclosure, but thedisclosure is not limited to the embodiments, and a plurality ofvariants may be made within the range of the claims, and the technicalconcept set forth in the specification and accompanying drawings.

What is claimed is:
 1. A power transmission apparatus, mounted on avehicle, the power transmission apparatus comprising: a rotating shaft,extending along a width direction of the vehicle, and used fortransmitting power to a drive wheel of the vehicle; a gear, disposed onthe rotating shaft, and used for transmitting power to the rotatingshaft; a clutch, used for disconnecting or connecting the powertransmitted by the rotating shaft to the drive wheel; a gear chamber,used for accommodating the gear; a clutch chamber, disposed adjacent tothe gear chamber in an axial direction of the rotating shaft, and usedfor accommodating the clutch; and a communicating portion, used forcommunicating the clutch chamber with the gear chamber, wherein a firstinclined surface facing toward the communicating portion is provided onan inner surface of the clutch chamber opposite to an outer peripheralsurface of the clutch.
 2. The power transmission apparatus according toclaim 1, wherein the communicating portion is a communicating holeformed on a wall portion between the gear chamber and the clutchchamber; and the power transmission apparatus comprising a ribprotruding from the wall portion lower than the communicating portiontoward the inside of the clutch chamber.
 3. The power transmissionapparatus according to claim 2, comprising another communicating portionformed on the wall portion, wherein the another communicating portion isformed at a position of the wall portion lower than the communicatingportion and the rib.
 4. The power transmission apparatus according toclaim 3, wherein the another communicating portion is formed at aposition higher than an oil surface of the gear chamber when the powertransmission apparatus operates.
 5. The power transmission apparatusaccording to claim 4, comprising an oil pump used for conveying oilstored in the gear chamber to the clutch chamber, wherein an oilstrainer connected to the oil pump is accommodated in the gear chamber.6. The power transmission apparatus according to claim 3, comprising anoil pump used for conveying oil stored in the gear chamber to the clutchchamber, wherein an oil strainer connected to the oil pump isaccommodated in the gear chamber.
 7. The power transmission apparatusaccording to claim 2, comprising an oil pump used for conveying oilstored in the gear chamber to the clutch chamber, wherein an oilstrainer connected to the oil pump is accommodated in the gear chamber.8. The power transmission apparatus according to claim 1, comprising anoil pump used for conveying oil stored in the gear chamber to the clutchchamber, wherein an oil strainer connected to the oil pump isaccommodated in the gear chamber.
 9. The power transmission apparatusaccording to claim 8, wherein the gear chamber comprising a gearaccommodating portion accommodating the gear and a straineraccommodating portion accommodating the oil strainer; the gearaccommodating portion and the strainer accommodating portion aredisposed adjacent to each other in the axial direction of the rotatingshaft, and boundary portions of the gear accommodating portion and thestrainer accommodating portion are in communication with each other; andthe strainer accommodating portion is disposed at a side closer to acenter in the axial direction of the rotating shaft than the gearaccommodating portion disposed.
 10. The power transmission apparatusaccording to claim 7, wherein the gear chamber comprising a gearaccommodating portion accommodating the gear and a straineraccommodating portion accommodating the oil strainer; the gearaccommodating portion and the strainer accommodating portion aredisposed adjacent to each other in the axial direction of the rotatingshaft, and boundary portions of the gear accommodating portion and thestrainer accommodating portion are in communication with each other; andthe strainer accommodating portion is disposed at a side closer to acenter in the axial direction of the rotating shaft than the gearaccommodating portion disposed.
 11. The power transmission apparatusaccording to claim 6, wherein the gear chamber comprising a gearaccommodating portion accommodating the gear and a straineraccommodating portion accommodating the oil strainer; the gearaccommodating portion and the strainer accommodating portion aredisposed adjacent to each other in the axial direction of the rotatingshaft, and boundary portions of the gear accommodating portion and thestrainer accommodating portion are in communication with each other; andthe strainer accommodating portion is disposed at a side closer to acenter in the axial direction of the rotating shaft than the gearaccommodating portion disposed.
 12. The power transmission apparatusaccording to claim 5, wherein the gear chamber comprising a gearaccommodating portion accommodating the gear and a straineraccommodating portion accommodating the oil strainer; the gearaccommodating portion and the strainer accommodating portion aredisposed adjacent to each other in the axial direction of the rotatingshaft, and boundary portions of the gear accommodating portion and thestrainer accommodating portion are in communication with each other; andthe strainer accommodating portion is disposed at a side closer to acenter in the axial direction of the rotating shaft than the gearaccommodating portion disposed.
 13. The power transmission apparatusaccording to claim 12, wherein a protruding portion is formed on aninner surface of the strainer accommodating portion near the boundaryportion; and the protruding portion comprises a second inclined surface,and the second inclined surface is inclined in such a manner that itsposition becomes closer to a far side of a rotating direction of thegear in a direction farther away from the boundary portion.
 14. Thepower transmission apparatus according to claim 11, wherein a protrudingportion is formed on an inner surface of the strainer accommodatingportion near the boundary portion; and the protruding portion comprisesa second inclined surface, and the second inclined surface is inclinedin such a manner that its position becomes closer to a far side of arotating direction of the gear in a direction farther away from theboundary portion.
 15. The power transmission apparatus according toclaim 10, wherein a protruding portion is formed on an inner surface ofthe strainer accommodating portion near the boundary portion; and theprotruding portion comprises a second inclined surface, and the secondinclined surface is inclined in such a manner that its position becomescloser to a far side of a rotating direction of the gear in a directionfarther away from the boundary portion.
 16. The power transmissionapparatus according to claim 9, wherein a protruding portion is formedon an inner surface of the strainer accommodating portion near theboundary portion; and the protruding portion comprises a second inclinedsurface, and the second inclined surface is inclined in such a mannerthat its position becomes closer to a far side of a rotating directionof the gear in a direction farther away from the boundary portion. 17.The power transmission apparatus according to claim 1, wherein theclutch chamber is a pair of clutch chambers respectively disposed at twosides of the gear chamber in the axial direction of the rotating shaft;the communicating portion respectively communicates the pair of clutchchambers with the gear chamber; and the first inclined surface is a pairof first inclined surfaces correspondingly provided in the pair ofclutch chambers respectively.
 18. The power transmission apparatusaccording to claim 2, wherein the clutch chamber is a pair of clutchchambers respectively disposed at two sides of the gear chamber in theaxial direction of the rotating shaft; the communicating portionrespectively communicates the pair of clutch chambers with the gearchamber; and the first inclined surface is a pair of first inclinedsurfaces correspondingly provided in the pair of clutch chambersrespectively.
 19. The power transmission apparatus according to claim 5,wherein the clutch chamber is a pair of clutch chambers respectivelydisposed at two sides of the gear chamber in the axial direction of therotating shaft; the communicating portion respectively communicates thepair of clutch chambers with the gear chamber; and the first inclinedsurface is a pair of first inclined surfaces correspondingly provided inthe pair of clutch chambers respectively.
 20. The power transmissionapparatus according to claim 9, wherein the clutch chamber is a pair ofclutch chambers respectively disposed at two sides of the gear chamberin the axial direction of the rotating shaft; the communicating portionrespectively communicates the pair of clutch chambers with the gearchamber; and the first inclined surface is a pair of first inclinedsurfaces correspondingly provided in the pair of clutch chambersrespectively.